function kangaroo(x1: number, v1: number, x2: number, v2: number): string {
    // Write your code here
    let position1:number = x1;
    let position2:number = x2;
    if (v2 < v1){
        for(let x=0; x<10000; x++){
            position1+=v1;
            position2+=v2;
            if(position1 === position2){
                return 'YES';
            } 
        }
    }
    return 'NO';
}